“That was Friday morning. He was last seen at eleven Friday night⁠—but was he seen then?”

“The porter⁠—”

“A night porter⁠—who had not previously seen Halliday. A man comes in, sufficiently like Halliday⁠—we may trust Number Four for that⁠—asks for letters, goes upstairs, packs a small suitcase, and slips out the next morning. Nobody saw Halliday all that evening⁠—no, because he was already in the hands of his enemies. Was it Halliday whom Madame Olivier received? Yes, for though she did not know him by sight, an imposter could hardly deceive her on her own special subject. He came here, he had his interview, he left. What happened next?”

Seizing me by the arm, Poirot was fairly dragging me back to the villa.